Q4. The current in a 484 W, 220 V heater operated at 200 V is
(a) 0.75 A
(b) 3/8 A
(c) 2 A
(d) 15/4 A

Q5. Two lamps of 100 W and 240 W rated for 220 V are placed in series and a 400 V applied across them. Then
(a) only 100 W lamp will fuse
(b) only 200 W lamp will fuse
(c) both the lamps will fuse
(d) no lamp will fuse

Q6. A coil of wire of resistance 50 Ω is embedded in a block of ice. What is the amount of ice melted in 1 s if a potential difference of 210 V is applied across the coil?
(a) 2.625 g
(b) 3.25 kg
(c) 4.12 kg
(d) None of the above

Q7. What is the maximum safe current flow in a 36 Ω, 4 W resistor?
(a) 0.47 A
(b) 0.39 A
(c) 0.57 A
(d) None of the above

Q8. Which of the following parameter will remain constant during charging and discharging of a capacitor?
a) Power
b) Current
c) Time constant
d) Voltage

Q9. What is the value of initial current while charging a capacitor?
a) High
b) Low
c) 0
d) Cannot be determined

Q10. A capacitor is charged to a voltage of 440V and has a resistance of 40 ohm. Calculate the initial value of charging current.
a) 10A
b) 0A
c) Infinity
d) 20A

S8. Ans(c)
Explanation: The time constant in a circuit consisting of a capacitor is the product of the resistance and the capacitance (which are fixed for a particular capacitor). Smaller the time constant, faster is the charging and discharging rate and vice versa.

S9. Ans(a)
Explanation: The initial current of a capacitor is very high because the voltage source will transport charges from one plate of the capacitor to the other plate.

S10. Ans(b)
Explanation: Initially, there’s 0V voltage in a capacitor. As the capacitor charges, the voltage increases. Since a voltage is proportional to current by ohm’s law, initial current is also equal to zero.